140 1 Cutting Action. angle of relief or clearance angle, to keep the tool clear of the work; A. the tutting angle, and c the tool angfe. The point c requires great strength for metal tooling, and as this makes A. very large, 'paring* cannot occur, but the material will be 'crippled,' either by compression, shear, or a combination of both. Sections parallel to F G will be in compression, and those parallel to E G in shear, and it will be evident that along of tool/ trv some section E F, the material will "be weakened to the greatest extent ; here then the shaving breaks so ranch as to curve up the face of the tool The direction of E r will depend on- the relative values of the compression and shear strengths of the material, Great heat is generated, due to molecular resistance and friction. A lubricant of soap and water** is • used for ductile materials like wrought iron, contained in a can placed above the tooi-t»ox, and led to the topi point by a wire, down which it * Or soda, if rusting is to be avoided.